1. Field of the Invention.
The present invention relates to modified rosins which are useful as binders in printing inks and coating compositions. More specifically, the present invention relates to urethane-modified esters of rosins and their use in lithographic printing inks.
2. Brief Description of the Prior Art
Rosins have been generally disclosed for use as binders in lithographic printing inks. Of particular interest here are the performance properties of lithographic printing inks, after they have been successfully applied to printed matter such as magazine covers. More specifically, the concern here is for squalene resistance. Printed ink is considered squalene resistant if there is no noticeable change in the dried printed ink when it is contacted with squalene. This demonstrates the ability of the ink to withstand lubricant matter secreted by, say, the sebaceous glands of the skin.
Generally, lithographic inks are used in printing processes that employ planographic plates to separate image from non-image areas. The image areas are preferentially wet by ink, and the non-image areas are preferentially wet by an aqueous fountain solution. During printing, the ink must remain sufficiently stable to transfer properly; yet the printed ink must rapidly dry to a solid.
Lithographic ink binders are selected on the basis that will ensure the attainment of all of the above properties. For example, the working properties of the inks can be ensured by controlling the extent to which the ink, by virtue of its binder, and an aqueous fountain solution interact to form a water-in-ink emulsion. The working and/or printing properties on the press at the prevailing press speed can be affected by this interaction. Generally, the ink must be sufficiently viscous in order to transfer without misting. Yet, it must not be so tacky as to effect picking off the printed matter, hence it must have good solubility in the appropriate solvents. Also, the printed ink must dry rapidly and in this case must have good squalene resistance.
As can be seen from the foregoing, the selection or the preparation of ink ingredients, and in this case the ink binder, that will meet the above requirements is a difficult task. By this invention, one such type binder and inks formulated therewith are provided.